Surgical lasers are now commonly used in a variety of ophthalmic surgical procedures, including the treatment of ocular diseases and the correction of optical deficiencies. In these procedures, the surgical laser is often chosen as the tool of choice because of the ability of the laser to be accurately focused with great precision. In addition, the ability of the laser to be guided to designated locations within the eye, with precision and reliability, has enabled ophthalmic procedures to be performed throughout the eye.
Anatomical characteristics of the eye, however, can undermine the effectiveness of any laser procedure. In particular, this is so for ophthalmic laser surgery that is to be performed on tissue behind (i.e. posterior) the cornea. Specifically, the beam of a laser can be significantly degraded by wrinkles that may be induced predominantly on the posterior surface of the cornea of an eye, when the eye is being stabilized by a contact element. The effect of these wrinkles becomes most acute when the laser beam is used for procedures on tissues in the deeper regions of the eye beyond the cornea, such as the lens or the retina.
Typically, when an eye stabilizing device is used, it is placed against the anterior surface of the eye and is pressed in a posterior direction. As a consequence, tissue in the eye may be squeezed in a manner that will cause wrinkles to be created primarily on the posterior surface of the cornea of the eye. These wrinkles can then cause an undesirable refraction, dispersion and degradation of the laser beam, as well as other adverse optical effects, as it passes through the cornea. An additional drawback caused by dispersion of the laser beam is the possibility of unintentionally damaging non-targeted tissue.
Typically, during an ocular laser procedure, an interface device is employed to dock a laser system with a patient's cornea. Once docked, the anterior corneal surface is fixed in four dimensions (i.e. x, y, z and over time t) relative to the laser system. As indicated above, prevention of folds on the posterior corneal surface can be important for procedures extending posteriorly to the cornea.
The shape of the anterior surface of the cornea and the variation of corneal shape and size across the patient population can complicate the selection and application of a suitable contact surface. In this regard, at the macroscopic level, the anterior surface of the cornea generally includes two regions. These include a central region with a relatively steep curvature that is surrounded by a peripheral region have a flatter curvature. The actual size and curvature of the regions varies from patient to patient.
Currently used patient interfaces typically have either non-deformable solid or liquid contact surfaces. Solid interfaces have typically been used in corneal procedures while liquid interfaces have more recently been developed for use in cataract surgery. Typically, for these procedures, a patient interface that establishes contact with both the central and peripheral regions of the cornea is used. Recall that these regions differ in curvature. Because of this curvature difference, when a solid interface is used to contact both the central and peripheral regions of the cornea, a substantial flattening of the central region can occur, resulting in corneal deformation and, in some cases, wrinkle formation on the posterior corneal surface. Specifically, current all-purpose solid patient interfaces designed to accommodate a wide patient population with its inherent anatomical variations typically include a one-size-fits-all curvature of 32 diopters.
In addition to stabilizing and aligning the cornea relative to the laser system, it is also desirable to stabilize the eye by reducing ocular movements induced by the patient's heartbeat. In particular, a number of corneal applications such as LASIK flaps, intrastromal relaxing incisions, and others are sensitive to these heartbeat induced ocular movements. In some cases, it may be desirable to include one or more direct contact areas between a solid, non-deformable part of a patient interface substantially over (or in the vicinity of) a diameter which prevents movement induced by heartbeat in the areas of the cornea targeted by these procedures. In this regard, corneal flap incisions that are performed as part of LASIK surgery rarely have diameters larger than 9.5 mm. Meanwhile, cataract incisions such as Limbal Relaxing Incisions (LRI) may be performed more peripherally than the incisions cited above, and are typically less sensitive to heartbeat induced ocular movements.
In light of the above, it is an object of the present invention to provide a patient interface that can be used on patients within a patient population having differing corneal shapes and sizes. It is another object of the present invention to provide systems and methods for stabilizing a patient's eye for an ophthalmic laser treatment while minimizing cornea wrinkles in the cornea area where the treatment laser passes. It is yet another object of the present invention to provide systems and methods for stabilizing a patient's eye that reduces the adverse effects of heartbeat induced ocular movements. Yet another object of the present invention is to provide an adaptable patient interface and corresponding methods of use which are easy to use, relatively simple to implement, and comparatively cost effective.